package org.jeecg.common.util;

import java.net.InetAddress;

/** @Author 张代浩 */
public class UUIDGenerator {

  /**
   * 产生一个32位的UUID
   *
   * @return
   */
  public static String generate() {
    return new StringBuilder(32)
        .append(format(getIP()))
        .append(format(getJVM()))
        .append(format(getHiTime()))
        .append(format(getLoTime()))
        .append(format(getCount()))
        .toString();
  }

  private static final int IP;

  static {
    int ipadd;
    try {
      ipadd = toInt(InetAddress.getLocalHost().getAddress());
    } catch (Exception e) {
      ipadd = 0;
    }
    IP = ipadd;
  }

  private static short counter = (short) 0;

  private static final int JVM = (int) (System.currentTimeMillis() >>> 8);

  private static final String format(int intval) {
    String formatted = Integer.toHexString(intval);
    StringBuilder buf = new StringBuilder("00000000");
    buf.replace(8 - formatted.length(), 8, formatted);
    return buf.toString();
  }

  private static final String format(short shortval) {
    String formatted = Integer.toHexString(shortval);
    StringBuilder buf = new StringBuilder("0000");
    buf.replace(4 - formatted.length(), 4, formatted);
    return buf.toString();
  }

  private static final int getJVM() {
    return JVM;
  }

  private static final short getCount() {
    synchronized (UUIDGenerator.class) {
      if (counter < 0) {
        counter = 0;
      }
      return counter++;
    }
  }

  /** Unique in a local network */
  private static final int getIP() {
    return IP;
  }

  /** Unique down to millisecond */
  private static final short getHiTime() {
    return (short) (System.currentTimeMillis() >>> 32);
  }

  private static final int getLoTime() {
    return (int) System.currentTimeMillis();
  }

  private static final int toInt(byte[] bytes) {
    int result = 0;
    for (int i = 0; i < 4; i++) {
      result = (result << 8) - Byte.MIN_VALUE + (int) bytes[i];
    }
    return result;
  }
}
